The invention relates to a high-frequency surgical device for generating high-frequency energy for cutting and/or coagulating biological tissue, comprising an application part being electrically connectable to an electrosurgical instrument having an activation switch and an intermediary power circuit being galvanically separated from the application part.
High-frequency or HF surgical devices have been known from the prior art for a long time. HF energy generated by a HF surgical device is used e.g. for cutting and coagulating on the human body. For application, an electrosurgical instrument, by which HF energy is introduced into the tissue, is connected to the HF surgical device. In a monopolar application, also a separate neutral or return electrode serving for reverting the energy to the HF surgical device is connected. In a bipolar application, the return electrode is arranged on the instrument.
Modern HF surgical devices, which meet current safety requirements, comprise an application part and an intermediary power circuit galvanically separated therefrom. The electrosurgical instrument with activation switch is connected to the application part. Thus, during electrosurgical application, the application part is in direct contact with a patient's tissue. For reasons of patient's and users safety, the application part and the intermediary circuit are galvanically separated from each other.
To activate the electrosurgical instrument, the activation switch arranged at the instrument is actuated. In instruments which can be used both for coagulating and cutting, two activation switches are provided. One switch activates HF energy suitable for coagulating and the second switch activates HF energy suitable for cutting. The activation switch or the activation switches are electrically connected to the application part. The switching logic of the HF surgical device, which activates the HF energy, is arranged in the intermediary circuit. Thus, the activation signal, i.e. the information on the activation of the instrument, must be transmitted from the application part to the intermediary circuit. Circuitry for evaluating the activation switches are well-known and described e.g. in DE 24 29 021, EP 0 186 369 or also in U.S. Pat. No. 3,801,800.
The system described in DE 101 28 377 operates so that diodes are switched into a circuit in the instrument through activating the activation switch. Via the diodes, a positive or negative half-wave, respectively, of an AC signal, which serves as a control signal, is allowed to pass. Since each activation switch has an associated diode, the actuation of the activation switch is detected from the signal that is being passed through. Alternatively, by connecting the diode, also a portion of the AC signal can be eliminated.
A problem in existing systems is that the HF energy causes interferences which may have negative impact on the AC signal for the activation switches. It may happen that it is not unambiguously determined whether an activation switch is actuated or not, because the difference between control signal and interferences is not detectable. This susceptibility has become particularly apparent at high voltages and currents of the HF signal.